In recent years, an information processing technology and information and communication technologies have been developing significantly. Accordingly, information processors including personal computers and portable information terminals are unevenly distributed throughout the real world, such as offices and homes. Under these circumstances, it is expected that a system for actively utilizing the situation of the real world (for example, positions of objects and users in the real world) will be realized.
Accordingly, the use of a system for measuring 3D-position/orientation of an object in the real world has been considered (hereinafter the system is referred to as a 3D-position/orientation measuring system). Specifically, the use of a 3D-position/orientation measuring system using a method applying a magnetic conversion phenomenon (when a coil is placed in a magnetic field, a current is induced to the coil (hereinafter, a method using magnetic conversion is referred to as a magnetic method)), has been considered (see U.S. Pat. No. 3,868,565 “Object tracing and orientation determination means, system and process).
In a 3D-position/orientation measuring system using a magnetic method, a user can freely move an object, and thus a user's operation can be simplified. However, the 3D-position/orientation measuring system using a magnetic method has a problem of being subject to the ambient environment which disturbs a magnetic field, such as electronic equipment, metallic components, and geomagnetism. That is, a measured value of an object measured by a magnetic 3D-position/orientation measuring system includes an error, which results from the ambient environment. Therefore, the magnetic 3D-position/orientation measuring system is not suitable for the situation where the ambient environment cannot be specified.
In order to overcome this problem, it has been considered to use an optical, ultrasonic, or mechanical 3D-position/orientation measuring system, in which the 3D-position/orientation of an object can be measured without being affected by the ambient environment, such as a magnetic field. However, in the 3D-position/orientation measuring system using an optical, ultrasonic, or mechanical method, a measurement range is limited or a user's operation become complicated, compared with the magnetic method.
That is, in an optical 3D-position/orientation measuring system, image of three or more markers is taken by a camera, and 3D-position/orientation is measured based on image information of the markers. On the other hand, an ultrasonic 3D-position/orientation measuring system includes a transmitter and a receiver, in which 3D-position/orientation is measured based on the pressure and transport speed of an ultrasonic wave, which is transmitted from the transmitter and is received by the receiver.
Therefore, in an optical or ultrasonic 3D-position/orientation measuring system, when visual information (image information of markers) is hidden behind a hand or other objects or when an ultrasonic wave cannot be detected, the 3D-position/orientation of an object cannot be measured (because of limited measurement range). Thus, a user has to operate a device while always being conscious of visual information and occlusion of ultrasonic waves.
Also, a mechanical 3D-position/orientation measuring system includes a mechanical movable portion, such as a polyarticular arm, in which 3D-position/orientation is measured based on the movement of the movable portion. Accordingly, the mechanical 3D-position/orientation measuring system has problems in that a measurement range is narrow (the range is limited within the movable range of the movable portion), and that the cost increases in order to ensure some accuracy. In order to overcome the problems in such a mechanical method, a plurality of inexpensive mechanical 3D-position/orientation systems may be used at the same time. In this case, however, new problems occur, that is, measurement accuracy is degraded and user's operation becomes complicated, compared with the case where another method is used.
As described above, a magnetic 3D-position/orientation measuring system has advantages in that a user's operation can be simplified and a measurement range is wide. On the other hand, other types of systems (for example, optical, ultrasonic, and mechanical systems) have advantages in that a reliable measured value which is not affected by the ambient environment can be obtained. A system having the combination of these advantages has not been devised.